Electric-arc lamp.



-N o. 755,815. PATENTED MAR. 29, 1904.

E. THOMSON. ELEGTRIG ARC LAMP.

APPLICATION FILED AUG. 19, 1901.

N0 MODEL. 2 SHEETS-SHEET 1.

m M New FL I.

\A/I JEEEEE. IVE ITUR Elihu Thomson PATENTED MAR. 29, 1904.

E. THOMSON. ELECTRIC ARO LAMP. APPLICATION PI LED AUG. 19, 1901.

2 SHEETS-SHEET 2.

JE LTU '5 Elihu Thom son Patented March 29, 1904.

FUNITED STATE-s P TENT OFFICE.

ELIHU THOMSON, OF SWAMPSOOTT, MASSACHUSETTS, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 755,815, dated. March 29, 1904.

Application filed August 19, 1901i Serial No. 72,471. (No model.)

To all whmn it may concern.-

Be it known that I, ELII-IU THOMSON, a citizen of the United States, residing at Swampscott, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Arc-Lamps, of which the following is a specification.

This invention relates to electric lighting, and especially to arc-lamps of the inclosed-arc type operated by direct current on constantpotential circuits.

The object of the invention is to produce a stable arc of considerable length without much, if any, resistance in series with each lamp, since it is Well known that ordinary constant-potential arc-lamps are liable to be unstable unless a resistance is interposed in the lamp branch. It has been found that this instability can be largely obviated by using a selfinductive coil in place of the resistance. I adopt this expedient; but I also utilize the self-inductive coil to exert a regulating action upon the lamp, whereby a tendency of the arc to rupture is immediately accompanied by a shortening of the arc, while a rapid rise in the current produces a lengthening of the are. To this end the self-induction coil or coils are connected in series with the arc and are located upon a core common to them and to a closed or short-circuited conductor. The movable carbon is actuated by an armature which is permanently polarized by a series solenoid. The armature is adjacent to the core aforesaid, so as to be attracted by the changing strength of the. core due to the fluctuating influence of the closed conductor as the current rises and falls. The operation of the lamp mechanism is thus rendered very prompt, and by so constructing the parts as to give the armature considerable range of movement without much change of the field of force which actuates it a long are can be maintained.

In the accompanying drawings, Figure lis a side elevation of a lamp embodying my invention, the frame being in section. Fig. 2 is an elevation of the same lamp looking in the direction of the arrow in Fig. l.

The frame A, cap B, globe O,' and carbons DD are all of the usual construction. To the cap is secured a core E, preferably made of laminated iron and forming a substantially rectangular frame, having upright sides 6, a

lower transverse member 6', and two upper transverse members 6 With a gap between their ends to increase the reluctance of the magnetic circuit and decrease the self-inductive effect of the wire coils F, which surround the upright sides 6. The coils are in series with the carbons D D.

On the lower transverse member 6 of the core is placed a heavy closed band or coil G of some good conductor, such as copper. This is made quite massive and is the seat of in- .duction-currents on any tendency to vary the magnetic lines of force threaded through it.

Near the coilG is an armature H, made of soft iron and preferably laminated. It has bent end portions h extending along near the corners e of the core E. The middle portion of the armature passes through an open coil or solenoid I in series with the coils F and the arc. There is room inside the coil for the armature to have considerable play, the armature being mounted on a frame K, suitably pivoted at k to the frame A of the lamp and movable up and down. To partly balance the Weight of the frame, a coiled spring L is attached to it and to the frame A, being preferably adjustable by means of a screw and nut, as shown; A link M connects the frame K with the pivoted dog-clutch N of the lamp, which grips and lifts the carbonwhen raised.

The operation is as follows: The passage of the current through thecoils F magnetizes the core E, upon which the coils are mounted, the polarization being in one direction through the core. Any variation of this magnetic the coils F is stable, then .this attraction is uninfluenced by the magnetism of the core itself, provided such magnetism be well below saturation. The are is therefore struck by the attraction of the armature H upward, due to its magnetization by the coil I. If the arc becomes too long and begins the process of rupturing, the current is weakened, and the magnetizing effect of the coil I on the armature H is lessened, so that the armature drops and releases the clutch. This result is hastened by the interoperation of the coils F and the closed band G, as follows: Vhen the current begins to die away, the self-induction of the coils F sets up an electromotive force, assisting the line-current and tending to maintain the are; but at the same time the magnetic flux in the core E will fall. This fluctuation in the field of force in which the closed coil G is located sets up a current in said coil which tends to oppose the fall of magnetic flux in the core. The consequence is that free magnetism operates upon the horizontal member a of the core, forming poles at the points 6 of the same name as the polarity in the armature H, which will therefore be repelled. Consequently the action of the armature in shortening the arc to prevent rupture is exceedingly prompt and rapid. If, on the other hand, the arc is too short and the current risesrapidly, the armature is lifted higher, but the self-induction of the coils F again opposes a counter electromotive force tending to cut down the line-current. The magnetic flux in the core will increase, however, setting up a counter-current in the coil G, which tends to polarize the member a of the core E in such manner as to attract the armature H, thus assisting it to lengthen the are. The shape of the poles IL with respect to the core E is such that the magnetic pull with a given current is substantially uniform in all positions of the armature or sufficiently so not to interfere with the operation of the lamp.

It appears from the foregoing description that there are three factors which operate to insure a stable are: first, the self-induction of the coils F, tending to oppose any change in linecurrent, and thus delay the change in' the arc until the lamp mechanism operates; second, the varying magnetic attraction between the polarized armature H and the iron core E, and, third, the polarizing effect of the closed coil G on the horizontal member a of the core assisting in attracting or repelling the armature. Practical tests show that these actions occur almost constantly, so that the readjustments are frequent and rapid. The lag in the current due to theself-induction coils F is suf ficient to give the solenoid I and the closed self-induction coil Gr time to shift the carbon before the arc ruptures. To this end it is desirable that the lever K and armature H be not of too great mass, but light enough to move freely and promptly.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In an arc-lamp, means for opposing temporarily any change in line-current, means varying with said current for varying the arc, and means unconnected with the line for assisting the arc-varying means.

2. In an arc-lamp, a self-induction coil in series with the are, means varying with the line-current for varying the arc, and means unconnected with the line for assisting the arc-varying means.

3. In an arc-lamp, means for temporarily opposing any change in line-current, a solenoid in series with the are, an armature polarized by said solenoid and connected with the movable carbon, and means unconnected with the line for assisting the arc-varying means.

4. In an arc-lamp, means for temporarily opposing any change in the line-current,means for varying the arc in accord with the varia tion of the line-current, and a closed coil operating to assist said arc-varying means.

5. In an arc-lamp, the combination with the movable carbon, of an armature connected therewith, a magnetic core adjacent to said armature, means for varying the magnetic flux in said core in accord with the changes in line-current, and a closed coil or secondary for varying the amount of magnetism diverted from said core through said armature.

6. In an arc-lamp, the combination with a self-induction coil in series with the arc, of a polarized armature connected with the movable carbon, and a closed coil operating to assist the movements of said armature.

7. In an arc-lamp, the combinatiorywith a self-inductive coil in series with the arc, of a solenoid also in series with the are, an armature movable in said solenoid and polarized thereby, a magnetic core adjacent to said armature and magnetized by said self-inductive coil, and a closed coil on said core.

8. In an arc-lamp, a core magnetized by the line-current, and means for varying the length of the arc comprising a closed coil responsive to changes in the magnetic flux in said core.

9. In an arc-lamp, a movable polarized ar' mature for varying the length of the are, a stationary solenoid for varying themagnetism of said armature in accord with the line-current variation, a core in the field of force of said armature, and means for polarizing said core.

10. In an arc-lamp, a movable polarized armature for varying the length of the are, a stationary solenoid for varying the magnetism of said armature, a core adjacent to said armature, and a closed coil on said core.

11. In an'arc-lamp, a movable polarized armature for varying the length of the arc, means for varying the magnetism of said armature in accord With the line-current, a magnetized core adjacent to said armature, means for varying the magnetic flux in said core in accord With the line-current, and means responsive to such Variation for inducing free poles in a portion of said core adjacent to said armature. 10

In Witness whereof I have hereunto set my hand this 15th day of August, 1901.

' ELIHU THOMSON.

Witnesses:

DUGALD MoK. MoKILLoP, JOHN J. WALKER. 

